This invention relates to an auxiliary apparatus to be used at the time of sampling only blood serum from a centrifuged blood sample.
Before performing various types of blood tests such as a biochemical analysis, etc., blood contained in a specimen container such as a test tube is subjected to a centrifugal treatment, and then blood serum contained therein is sampled and dispensed into several test vessels.
In general, the centrifuged blood sample in a test tube is definitely separated into blood serum and a blood clot by means of a separating medium such as silicon. More specifically, in the test tube, the centrifuged blood sample is separated into the blood serum, the separating medium and the blood clot arranged in this order from above.
To sample the blood serum in the test tube, a sampling/dispensing tip with a sharply tapered, hollow and conical tip portion is inserted into the test tube from above. When the tip portion reaches the blood serum, the tip sucks only the blood serum using an air sucking mechanism, etc., and then is raised and kept at a raised position.
After the sampling operation, the sampling/dispensing tip is shifted to a predetermined position, where the blood serum contained therein is discharged (i.e. dispensed) into several predetermined test vessels.
The blood sample components (i.e. the blood serum, the blood clot, the separating medium) contained in the test tube after the centrifugal treatment do not always show clearly separated states, but may show abnormal states.
FIGS. 15 to 17 show such abnormal states of blood sample components (blood serum 2, a blood clot 3, a separating medium 4) contained in a test tube 1. FIG. 15 shows a case where the separating medium 4 has a separation surface A with irregularities, which contacts the blood serum 2. FIG. 16 shows a case where a separation surface B inclines by a certain angle relative to the axis 0 of the test tube 1. FIG. 17 shows a case where the separation surface of the separating medium 4 is relatively flat and horizontal, and fibrin 5 which may cause clogging of a sampling/dispensing tip (not shown) is floating in the blood serum 2.
When the separating medium 4 assumes a state as shown in FIGS. 15 or 16, the level at which the separation surface of the separating medium 4 is formed cannot definitely be determined. In other words, the level of the separation surface of the separating medium 4 or that of a deepest portion of the blood serum 2 will assume different values when it is sensed by a sensor (not shown), etc. several times. If the sampling/dispensing tip is lowered to a tip insertion limit set on the basis of such an indefinite sensed level, a lower open end portion of the tip may well thrust into the separating medium 4 and be clogged with the medium.
To avoid this, the prior art takes a measure, for example, to set the tip insertion limit to a level much shallower than the sensed level. This measure, however, makes it impossible to sample all blood serum 2 in the test tube 1, and inevitably limits the effective use of valuable blood serum obtained by a centrifugal treatment.
On the other hand, in the case of FIG. 17 where fibrin is floating in the blood serum 2, the fibrin may be sucked into the open end of the sampling/dispensing tip to thereby clog the same. As a result, it is possible that clogging of the tip will start immediately after the sampling of the blood serum 2. In this case, the aforementioned measure to set the insertion limit of the tip to a much shallower level is quite useless.